Target electrode support for a scan conversion tube



;May 31, 1966 R. J. DOYLE TARGET ELECTRODE SUPPORT FOR A SCAN CONVERSION TUBE 2 Sheets-Sheet '1 Filed March 22, 1963 y 31, 1965 I R. J. DOYLE 3,254,250

TARGET ELECTRODE SUPPORT FOR A SCAN CONVERSION TUBE Filed March 22, 1963 IO 4 p s1 7o 75 66 PHOSPHDR'\ 5/4 53 56 5 5e 57 PHOTOCONDUCTOR 55 5| Q 72 73 8 67a ssa 64o Fig.8.

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97 9| 95 d1 6 ll! Fig.l3- Fig.l4. Fig.l5. WITNESSES INVENTOR Ma W Robert J. Doyle 2 Sheets-Sheet 2 CONVERSION TUBE Robert J. Doyle, Elmira, N.Y., assignor to Westinghouse Electric Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Filed Mar. 22, 1963, Ser. No. 267,164 6 Claims. (Cl. 313-65) This invention relates to an electron discharge device and more particularly to mounting structure for electrodes within electron discharge devices.

One particular application of this invention is in storage cathode-ray tubes wherein information is written onto a storage target by electron bombardment by a writing electron beam on one side of a storage electrode, and information is read-out by the action of a reading electron beam directed onto the other side of the target electrode. The principles of my invention may be employed in a scan conversion tube such as described in US. Patents 2,900,555 and 2,928,969 by R. J. Schneeberger and assigned to the same assignee as the present invention. Another particular application of my invention is in a device such as described in US. Patent 3,124,715 which issued on March 10, 1964.

In all of the devices referred to above, the target electrode normally is comprised of a thin delicate film mounted within the tube and having an electrical connection to the outside of the tube. In the prior art, several techniques have been utilized to mount the target electrode within the tube such as mounting the film upon a support ring and then securing the target electrode to one of the electron gun assemblies by spring mounting. These 'prior contructions resulted in several disadvantages, such as, diflioulty in obtaining the proper spring compression during seal-in and the possibility of placing a strain in the thin target fi-lm. Another problem involved in this technique of mounting the target electrode was the difiiculty of inserting and handling the assembly when mounted on top of the electron gun structure. This target is mechanically independent of all electron guns.

Another important mounting consideration is that a minimum number oi metal parts should be utilized in inounting the target electrode so as to keep the capacitance between the input and output sections at a minimum, and also keep the output capacitance of the device at a minimum.

i It is accordingly an object of this invention to provide an improved electrode mounting means for an electron discharge device.

' United States Patent It is another object to provide an improved electrode inounting means for a scan conversion storage tube.

It is another object to provide an improved mounting arrangement for a target electrode of electron bombardment induced conductivity material within a scan con version tube.

It is another object to provide an improved scan conversion tubein which a minimum of capacitance is provided between the input and output system and in which the output capacitance is a minimum.

In accordance with the above objects, this invention provides a mounting arrangement for including a ring of insulating material and securing a target electrode element within an envelope and the provision of suitable electrical .conductive means associated with said insulating ring assembly to provide electrical con-tact to the target from the exteriorof the envelope.

These and other objects are effected by my invention as will be apparent from the following description taken in conjunction with the accompanying drawings, in which:

FIGURE 1 is a schematic representation of a storage tube embodying my invention;

3,254,250 Patented May 31, 1966 FIGURE 2 is a front view of the target electrode assembly taken along the line I'I--'II of FIGURE 1;

FIGURE 3 is an enlarged plan view of a mounting ring portion of the target assembly shown in FIGURE 2;

FIGURE 4 is a sectional view taken along the line IV IV of FIGURE 3;

FIGURE 5 is an enlarged plan view of the space rings surrounding the target member in FIGURE 1;

FIGURE 6 is a sectional view of FIGURE 5 taken along the line VI-VI;

FIGURE 7 is a plan view showing the opposite surface of the member illustrated in FIGURE 5;

FIGURE 8 is a sectional view, taken along the line VIII-VIII of FIGURE 2;

FIGURE 9 is a plan view of a modified target assembly that may be incorporated in the tube shown in FIGURE 1;

FIGURE 10 is a sectional view taken along the line X-X of FIGURE 9;

FIGURE 11 is an enlarged view of the support ring illustrated in FIGURE 9;

FIGURE 12 is a sectional view. taken along the line XIIXII ot FIGURE 11; and

FIGURES 13, 14 and 15 illustrate support and holding pins associated with the target illustrated in FIG- URE 9.

Referring in detail to FIGURE 1, a scan converter tube is illustrated in which information is written on one side of a target 20 and the information is read-out from the other side of the target. The device consists of an evacuated envelope 10 of a suitable material such as glass. The envelope 10 consists of a tubular body portion 11 closed at one end by a base 112 and the other end by a base 14 through which lead-in members are provided to supply-voltages to the majority of the electrodes within the envelope 10. The tube may be considered to include two sections, namely a writing section, the section above the target 20 in FIGUREl, and a reading section, the section below the target 20 of the FIGURE 1. The planar storage target 20 is positioned perpendicular to the axis of the tubular portion 11 off the envelope 10 and substantially centrally located within the envelope 10.

Within the envelope 10, there is mounted a Writing electrongun structure 22 in the'upper portion of the envelope 10 forgenerating a high velocity beam. A reading beam electron gun 24 is provided in the lower portion of the envelope 10 for providing a low velocity reading beam. The target assembly 20, as illustrated in FIG- URE 8, includes a fiber-optic support plate 51 having an electrical conductive coating 53- on the Write-in side and a similar coating 55 on the read-out side of the fiberoptic support plate 51. A layer 54 of a suitable phosphor material is provided on the conductive coating 53. The

high velocity electron beam generated by the electron gun 22 is directed onto the phosphor layer 54. A photoconductive storage layer 57 is provided on the conductive coating 55. The photoconductive layer 57 faces the reading electron gun 24 and the reading gun 24 scans this surface to read-out a charge image produced on the surface of the photoconductive layer 57 in response to light directed onto the photoconductive layer 57 via the fiber-optics 51 from the phosphor layer 54.

The writing gun 22 may be of any suitable type such as found in a cathode ray tube and includes at least a cathode 23, a control grid 25- and an accelerating grid 27.. The electrons generated by the electron gun 22 are accelerated to a velocity of about 10,000 electron volts and bombard the phosphor layer 54 to generate light therefrom. A suitable deflection and scanning means (not shown), is provided for the electron gun 22 so as to scan a raster in any suitable manner over the phosphor layer 54.

The reading gun 24 may be of the type found in a vidicon type pick-up tube and provides a low velocity beam for scanning the layer 57. In the specific embodiment shown, the electron gun is of the type commonly used in the vidicon and includes at least a cathode 31, a control grid 33 and an accelerating electrode 35 for generating an electron beam which approaches the photoconductive layer 57 at a velocity of about 5 to 50 electron volts. Suitable focusing and deflection means (not shown) may also be provided on the exterior portion of the envelope or as an integral part of the electron gun, to provide the necessary scanning and focusing as required in this type of device. The type of electron gun utilized is not a part of this invention, and this invention is directed to the mounting assembly associated with the target assembly 2! in such a tube. It should also be noted that in addition to using an electron gun as the writing source, an input photocathode could be utilized and an input light directed onto the photocathode. The electron image generated by the photocathode could be focused onto the phosphor layer 54 in a Well-known manner.

Now, referring in detail to the target assembly 20, the fiber-optic plate 51 provides thousands of glass fibers having their axes parallel to the tube axis. The plurality of glass fibers are fused together side by side so that each fiber can pick up light on one end faceand deliver it to the other end face. The fiber-optic bundle behaves as a lens having a numerical aperture of approximately .7 such that an image implanted on one end surface is transferred through the fiber to the other surface with almost no loss of brightness and with very little resolution loss. This feature enables the fiber-optic member 51 to provide electrical separation of the write and read sections of the tube. Each of the glass fibers in the bundle usually consists of a core portion of a suitable glass having a high index of refraction and a jacket portion surrounding the core portion. The jacket portion normally consists of a glass of a lower index of refraction than that of the core. It is also possible to provide light absorptive coatings on the jacket to prevent interference. In the specific embodiment here, the core portion should be less than .001 inch to provide the desired resolution in this type of device.

In the fabrication of the target 20, the fiber-optic plate 51 is optically polished and cleaned and then the light transmissive electrically conductive layers 53 and 55 are deposited upon the two surfaces of the plate 51. When the desired resistance of the layers 53 and 55 has been obtained, which is normally about 100 to 400 ohms per square, the remaining coatings 54 and 57 are deposited. The conductive layers 53 and 55 cover substantially the entire face or surface of the plate 51 as indicated in FIGURE 8. There are several suitable materials, such as stannic oxide and gold, that may be used for the coatings 53 and 55. The layers 53 and 55 must be substantially transparent to the radiation emitted by the phosphor layer 54. The phosphor layer 54 of a suitable material may be cataphoretically deposited on one surface of the transparent conductive layer 53, or settled directly on the fiber-optic plate 51 and thereafter aluminized. The plate 51 is normally positioned in a special Teflon fixture to,

prevent deposition of the phosphor material on an outer peripheral portion 56 of the layer 53. This annular exposed surface portion 56 is provided to make an electrical contact to a metallized clamping ring 60.

When the phosphor coating 54 is dry, the reverse side of the fiber-optic plate 51 is provided with a suitable storage photoconductor member 57 such as a mixture of arsenic and selenium. The member 57 may include a layer of arsenic and selenium with a layer of antimony trisulfide deposited on the exposed surface of the arsenic and selenium layer. A specific example of a suitable example storage photoconductive member 57 is more fully described in US. Patent 3,046,431, entitled Storage System by J. Nicholson, issued July 24, 1962 and assigned to the same assignee as this invention. Here, again, a fixture is utilized so that an outer peripheral portion 58 tion 58 is provided to make an electrical contact to a metallized clamping ring 60.

The fiber-optic support plate 51 with the coatings 53 and 54 on one surface and the coatings 55 and 57 on the other surface is then mounted within a target holder assembly consisting of two clamping members 60 and 60a and a spacer ring 65. The spacer ring 65 centers the fiber-optic plate 51 within the holder assembly. The clamping rings 60 and 60a and the spacerv ring 65 may be of any suitable insulating material such as ceramic. In order to provide electrical contact from the conductive electrodes of the target 20, namely the coatings 53 and 55 to the exterior of the envelope, suitable electrically conductive metallizing coatings must be provided on the clamping rings 60 and 60a and the spacer ring 65. These conductive coatings may be of a suitable material, such as nickel or copper and may be placed thereon by any suitable method such as silk screening techniques.

Referring to FIGURE 3, the clamping member 60 shown therein consists of a substantially flat ceramic ring 62 with a metallized coating 64 provided on a side surface 61 of the ring 62. The inner diameter of the ring 62 adjacent the plate 51 is of a smaller diameter than the diameter of the plate 51 and of greater diameter than the coatings 54 and 57. The coating 64 consists of a first coating portion 66 annular in shape covering a portion of the surface 61 to make electrical and physical contact to the exposed annular portion 56 of the conductive coating 53 on the support plate 51. In addition, a second coating portion 67, arcuate in shape, covers the remaining portion of the surface 61 between the coating portion 66 and the outer edge of the surface 61 for about one-third of the ring 62. The first coating portion 66 makes electrical contact to the coating 56 on the support member 51 and the second coating portion 67 makes electrical contact to a conductive coating 70 provided on the spacer ring 65 as illustrated in FIG- URE 8. The clamping member 60 is provided with apertures 30a, 32a and 34a.

The washer or spacer ring 65 consists of a flat ceramic ring 69 having three openings 30b, 32b and 34b extending therethrough and spaced degrees apart. The electrically conductive coating 70 such as nickel is provided on one side surface of ring 69 and covers approximately one-third of the surface as indicated in FIGURE 5. The coating 70 also extends over into a radial opening or depression 40 in the outer surface of the ring 69 as indicated in FIGURE 6. A conductive coating 68 is provided on a portion of the opposite surface of the ring 69 as indicated in FIGURE 7 and covers about onethird of the surface and extends between the openings 32b and 34b. In addition, the conductive coating 68 extends over the outer edge of the ring 69 and into the radial opening 36. The radial depressions 36, 40 and 38 are disposed about the outer edge of ring 69 at about 120 degrees separation. The depression 38 is not provided with a conductive coating.

The upper clamping member 60 in FIGURE 8 is positioned so as to be in electrical and physical contact with the coating 70 by means of the coating portion 67 of the conductive portion 64. The lower clamping member 60a is positioned so that the second coating portion 67a of the conductive coating 64a is in contact with the coating 68 of the spacer ring 65 as indicated in FIGURE 8. The two metallized clamping rings 60 and 6011, the spacer ring 65 and the coated fiber-optic plate 51 are assembled as shown in FIGURES 2 and 8 with three stainless steel fastening members 71. The members 71 mechanically secure the members 60, 60a, 65 and 51 together. In mechanically securing the members together, electrical continuity is provided from the conductive layers 53 and 55 of the fiber-optic plate 51 to the two radially positioned holes 40 and 36, respectively. The conductive coatings 64, 64a, 68 and 70 do not cover the surface surrounding apertures 30, 32 and 34 to insure insulation of the members 71 from the conductive coatings. Thus, the target assembly is mechanically and electrically assembled and ready for insertion into the envelope.

Prior to insertion of the target assembly 20 into the envelope 10, three openings 72 are provided in the envelope wall portion 11. Eyelets or buttons 75 are fused within openings 72 in a well-known manner. The target 20 is then positioned within the envelope and pins 73 of a suitable material such as Kovar alloy are inserted through the openings in the eyelets 75 and into the radial depressions 36, 38 and 40. The pins 73 are then heliarc welded to the eyelets or contact buttons 75 to provide a vacuum-tight seal and mechanically secure the target within the envelope 10. Positive electrical contact to the exterior of the envelope 10 is also provided With respect to the pins 73 provided in the depressions 36 and 40.

In this manner, the fiber-optic target member 51 is firmly held within the center of the tube. It is easily inserted and fastened within the tube without scratching or contaminating the coatings on the fiber-optic plate. There is a minimum amount of capacitance between the input signal electrode 53 and the output signal electrode 55 due to the limited amount of metallic elements utilized in mounting the electrode. There is a reliable electrical contact between the conductive layer 53 and the conductive layer 55 to the exterior of the tube envelope and only a minimum number of parts and glass seals is required in the operation.

Another important consideration in this type of 'assembly is that thetarget assembly may be fabricated outside of the envelope and pretested prior to insertion in the tube. 'Another important advantage of this construction is that it is adaptable to accommodate thicker fiber-optic plates 5-1 and the dimensions are not critical. The capacitance between the input and output is a mini mum since there is a minimum of metal parts. In fact, the theoretical capacitance of inch thick fiber-optic target 1 inch diameter in space is about 10 picofarads and in a tube with the above mount the capacitance is found to be about 15.4 picofarads. Thus, the new assembly introduces only 5.4 picofarads capacitance between the input and output.

Referring now in detail to FIGURES 9 through 15, there is illustrated a target assembly 80 of the electron bombardment induced conductivity EBIC type in which a delicate film is mounted within the tube and provided with an electrical contact to the outside. The target assembly 80 includes a target mounting ring 81 of a suitable insulating material such as lava or ceramic.- The annular mounting ring 81 is provided with an inner annular seat portion 82. A conductive coating 83 is pro vided over the surface of the inner annular seat portion 82 and extends into a radial aperture 84 which extends through the ring 81 from the outer surface to the seat surface.

An EBIC film 94 is mounted on a support ring 85 and is positioned within the seat portion 82. The ring 85 may be of a suitable material such as Kovar alloy, Westinghouse Electric Corporation trademark for alloy of nickel, iron and cobalt. The EBIC target normally includes a conducting layer 92 of a suitable material such as aluminum with the film 94 of a material that exhibits electron bombardment induced conductivity such as potassium chloride deposited on the conducting layer. The conducting layer 92 may be used as the support layer on the ring 85 or if desired an aluminum oxide support layer may be used. This type of tube is more fully described in the previously mentioned Patents 2,900,555 and 2,928,969. The ring 85 is held within the ceramic' ring 81 by means of three holding pins 9-1 such as those illustrated in FIGURE 14. These holding pins 91 extend through radial apertures 93 and bear against the outer surface of support ring 85 within the mounting support. By providing a tight fit or deforming the copper pins 91, the target ring 85 will be held in the assembly. The assembly is then inserted into the envelope in a manner previously described and a pin 95 is inserted through the button 75. The pin 95 is then inserted into the opening 84 and makes electrical contact with the conductive coating 83 in the aperture '84 and the ring 85. The pin 95 has an eccentric point and is grasped with a pin vise and turned until the eccentric taper turns firmly down on the target ring 85 to insure good electrical contact. The pin '95 provides the electrical contact on the outside of the envelope '10 from the conductive layer 92 and the ring 85 of the EBIC film 94. Two other pins 97 are inserted into two depressions 99 and all the pins 95 and 97 are heliarc welded to the buttons 75 to provide a vacuum-tight seal.

While there have been shown and described what are at present considered to be the preferred embodiments of the invention, modifications thereto will readily occur to those skilled in the art. It is not desired, therefore,

that the invention be limited to the specific arrangement trode positioned within said tubular portion and transverse to the axis of said tubular wall portion, said electrode supported within said tubular wall portion by means of an annular ring of insulating material within which said electrode is mechanically secured thereto, electrically conductive support pins extending through said tubular wall portion and into depressions provided in said insulating ring to support said insulating ring and electrode within said envelope, electrical conductive coatings provided on said insulating ring and in contact with said electrode and at least one of said depressions so that at least one of said electrical conductive support pins provides an electrical contact on the exterior of the envelope for saidelectrode.

2. An electron discharge device comprising an 'envelope including a cylindrical envelope portion, an electrode positioned Within said cylindrical envelope portion, said electrode consisting of a thin disc-like member, a ring of insulating material surrounding said disc-like member with 'said disc-like member secured within said insulating ring so as to be mechanically secured therein, electrically conductive pin members extending through said cylindrical envelope portion and into depressions provided in the outer periphery of said insulating ring, an electrical conductive coating provided on the surface of said insulating ring making electrical contact to said disc-like member and the surface of-one of said depressions so that at least one of said electrical conductive pins provides both physical support for said electrode within said cylindrical envelope portion and electrical contact from said electrode to the exterior of said envelope.

3. An electron discharge device comprising an envelope including a cylindrical wall portion, a planar electrode positioned within said cylindrical wall portion lying in a plane substantially perpendicular to the axis of said cylindrical wall portion, said planar electrode comprising a fiber-optic support plate having two end faces, one of said faces having a first electrically conductive coating provided thereon and a layer of photoconductive material provided on said first conductive coating, the other end face having a second electrically conductive coating thereon and a coating of phosphor on said second conductive coating, said support plate having an outer cylindrical surface, an annular ceramic spacer, a first annular clamping member positioned about the outer cylindrical surface of said support plate, one side of said clamping member having a third conductive coating thereon in contact with a portion of said first conductive coating on said support plate, a second annular clamping member positioned on the opposite side of said support plate with respect to said first annular clamping member having a fourth conductive coating and in contact with a portion of said second conductive coating on said support plate, said spacer having a plurality of depressions about its outer circumference, a fifth conductive coating provided on said spacer surface in contact with said third conductive coating on said first clamping member and extending into one of said depressions, a sixth conductive coating on said spacer in contact with said fourth conductive coating on said second annular member and extending into another of said depressions, a plurality of electrical contact members extending through said cylindrical wall portion and into said depressions to support said electrode within said envelope and provide first and second exterior electrical terminals for said first and second conductive coatings on said end faces of said support plate.

4. An electron discharge device comprising an envelope including a cylindrical envelope wall portion, a target electrode positioned within said envelope and including a support disc of a fiber-optic material having a plurality of light transmitting fibers perpendicular to the end surfaces of said support disc, conductive coatings provided on both end surfaces of said support disc, a photoconductive layer deposited on one of said conductive coatings and providing an annular exposed conductive portion, a clamping member provided with a conductive coating positioned against said fiber-optic support disc so as to be in electrical and physical contact with said annular exposed conductive portion, a ceramic spacer surrounding said fiber-optic support disc and having a conductive coating in electrical and physical contact with said conductive coating on said clamping member, said spacer having a plurality of depressions with said conductive coating on said spacer extending into one of said depressions and a plurality of electrical conductive pins extending through said cylindrical envelope Wall portion into said depressions to support said target electrode and provide an exterior electrical terminal to said conductive coating in said depression.

5. An electron discharge device comprising an envelope including a tubular wall portion, an electrode positioned within said tubular wall portion, said electrode supported within said tubular wall portion by means of an insulating ring within which said electrode is mechanically secured, electrically conductive support members extending through said tubular wall portion and in contact with support portions on said insulating ring to support said insulating ring and electrode within said envelope, an electrical conductive coating providedon said. insulating ring in contact with said electrode and at least one of said support portions to that at least one of said electrical conductive support members provides an electrical contact on the exterior of the envelope for said electrode.

6. An electron discharge device comprising an envelope including a cylindrical envelope portion, a target electrode positioned within said cylindrical envelope portion, said target electrode consisting of a thin disc-like electron sensitive member, a first electron source positioned on one side of said target electrode for generating and directing electrons onto one surface of said target electrode, a second electron source positioned on the other side of said target electrode for generating and directing electrons onto the opposite surface of said target electrode with respect to said first electron source, an insulating means surrounding said disc-like member with said disc-like member secured within said insulating means so as to be mechanically secured therein, electrically conductive members extending through said cylindrical envelope portion and into depressed surface portions provided in the outer periphery of said insulating means and electrical conductive coatings provided on the surface of said insulating means making electrical contact to said electron sensitive member and one of said depressed surface portions so that said electrical conductive members provide both mechanical support for said target electrode within said envelope and electrical contact from said target electrode to the exterior of said envelope.

No references cited.

GEORGE N. WESTBY, Primary Examiner.

P. C. DEMEO, Assistant Examiner. 

6. AN ELECTRON DISCHARGE DEVICE COMPRISING AN ENVELOPE INCLUDING A CYLINDRICAL ENVELOPE PORTIONS, A TARGET ELECTRODE POSITIONED WITHIN SAID CYLINDRICAL ENVELOPE PORTION, SAID TARGET ELECTRODE CONSISTING OF A THIN DISC-LIKE ELECTRON SENSITIVE MEMBER, A FIRST ELECTRON SOURCE POSITIONED ON ONE SIDE OF SAID TARGET ELECTRODE FOR GENERATING AND DIRECTING ELECTRONS ONTO ONE SURFACE OF SAID TARGET ELECTRODE, A SECOND ELECTRON SOURCE POSITIONED ON THE OTHER SIDE OF SAID TARGET ELECTRODE GENERATING AND DIRECTING ELECTRONS ONTO THE OPPOSITE SURFACE OF SAID TARGET ELECTRODE WITH RESPECT TO SAID FIRST ELECTRON SOURCE, AN INSULATING MEANS SURROUNDING SIAD DISC-LIKE MEMBER WITH SAID DIS-LIKE MEMBER SECURED WITHIN SAID INSULATING MEANS 